Pinguicula utricularioides — Vorstman's Guide to the Carnivorous Plants

No photograph of this species under a Creative Commons licence or in the public domain is in the guide yet.

Identification

A plant with a very unusual leaf shape for the genus, hence the epithet: the summer leaf consists of a long slender petiole 10 to 25 mm long carrying a small, almost round blade only 2 to 4 mm across — a build recalling certain Utricularia species more than a butterwort. The winter rosette consists of narrow leaflets 5 to 20 mm long and 1 to 2.5 mm wide. The flower is scarlet red and 27 to 37 mm long including the comparatively short spur of 5 to 8 mm. Red is rare among Mexican butterworts, and combined with the stalked round blades this species is unmistakable.

Similar species

The other red-flowered Mexican species is Pinguicula laueana, from the Sierra Mixe in the same state; it is considerably larger, has broad ordinary butterwort leaves and a spur of four to four and a half centimetres against at most eight millimetres here. The difference is thus plain in both leaf and spur. No other species in Mexico has the long petiole with a small round blade. Anyone who believes they have seen this species should above all photograph well and record the locality.

The trap and how it works

A flypaper trap on a strikingly small surface. With a blade two to four millimetres across the catching area per leaf is minimal, though the plant probably compensates with a larger number of leaves on long stalks, spread through the moss. The blade carries the usual two gland types: stalked glands holding the prey with a sticky droplet, and sessile glands releasing enzymes on contact. Nothing has been published on the actual prey composition; given the dimensions it can only be very small insects and springtails.

Habitat and ecology

Little is known about the habitat. The only collection comes from Cerro Azul north of Niltepec in eastern Oaxaca, at an elevation given in the original record as six to seven thousand feet — roughly eighteen hundred to twenty-one hundred metres. That is the zone of humid montane and cloud forest in this part of the Sierra Madre del Sur (B1, R1). The stalked leaves point to growth among moss or in a loose damp layer, where an ordinary flat rosette would fare less well. More cannot be said with present data.

Distribution and elevation

Endemic to Mexico and known from one place in Oaxaca: Cerro Azul north of Niltepec. Our species list names Mexico, and the literature is more precise: eastern Oaxaca. This is a species that exists only as herbarium material from 1956. Whether the population is still present has not been established; there are no published refinds. That places the species in a category of its own within this guide: known, described, but unconfirmed in the field for seventy years.

Recorded (one-degree cells)

Distribution based solely on records at GBIF (Global Biodiversity Information Facility), not on TDWG regions — those are often far larger than the actual range. The light halo is the area around a record, the dark core the record itself. The darker square is the only one-degree cell — roughly a hundred and ten kilometres — in which the species has been recorded, from all GBIF records. This is coarser than for most species because hardly any record of this plant carries an accurate coordinate. It shows where the species has been seen, not where it occurs: an empty square means nothing.

Forms and variation

Because only one collection of this species exists, nothing whatever can be said about variation in the wild. No varieties have been described and there is no material with which populations could be compared. Nothing is known about natural hybrids either, and whether other butterworts occur on Cerro Azul with which crossing would be possible is unpublished. This is therefore a case in which the absence of observed variation says nothing about the species and everything about the thinness of the file.

Where and when to see it

For the field observer this is an assignment rather than a tip: anyone walking the mountain forest around Cerro Azul in eastern Oaxaca can watch for small red butterwort flowers above the moss. Search shaded, permanently damp slopes and banks between eighteen hundred and twenty-two hundred metres. Take no plants: a refind has value as a photograph, a coordinate and a date, not as a herbarium sheet. Report an observation to a Mexican herbarium or a local botanical institution.

Conservation status

Not assessed for the global IUCN Red List and not listed in CITES. Within this group this is the most extreme case of an empty file: one collection from 1956, one description from 1991, and no confirmed observation since. That does not mean the species has gone — the highlands of eastern Oaxaca are large and poorly surveyed — but it does mean that nothing can be said about its condition. The mountain forest in that area is under pressure from logging and conversion to farmland. The first step here is simple: search again at the original locality.

Scientific name

Pinguicula utricularioides | Zamudio & Rzedowski, 1991

Described by Sergio Zamudio and Jerzy Rzedowski in 1991, in the article "Dos especies nuevas de Pinguicula (Lentibulariaceae) del estado de Oaxaca, México", Acta Botánica Mexicana 14: 23–32, based on material collected by T. MacDougall in 1956. The type locality lies on Cerro Azul, north of Niltepec, in the Mexican state of Oaxaca, at 1800–2100 metres altitude. The name refers to the resemblance to the genus Utricularia (bladderwort): the long-petioled leaves of the summer rosette have a deeply spoon-shaped, almost bladder-like blade reminiscent of Utricularia traps, and the fused lower calyx lobe shows a similar structure.

World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.